My biological father was 20 and my mom was 15 when they had my sister...
And my mom was 20 (I do not remember) and my adopted dad was 20(I do not remember) when they had my brother
My mom is now 34, my dad is 39( he's going to be 40 soon)
I am 16 my sister is 17( going to be 18 soon) and my brother is 13
So its fine.. as long as it isn't 15 and 20... Like my mom and biological father...